Alternating-current induction motor



June 30, 1925.

T. TORDA ALTBRNATING CURRENT INDUCTION MOTOR 2 Sheets-Sheet 1 Filed June 7, 1922 June 30, 1925.

T. TORDA ALTIRNATING CURRENT INDUCTION IIOTOR Filed June 7 .1922 2 Sheets-Sheet 2 r & 74! .Z/loaare 743-4 I WWW Patented June 30, 1925.

PATENT ol-rlcs- THEODORE TOBDA, OF BUDAPEQT, HUNGARY.

- urmarmscunamrr nmucrzon moron.

Application filed June 7,

To all whom it may comm:

Be it known that I, Tnnononn TORDA, a citizen of Hungary, residing at Budapest, in Hungary, have invented certain new and useful Improvements in Alternating-Cur rent Induction Motors, of which the followin is a specification. i

' y invention which relates to alternating current induction motors and has among its objects the compensation of phase dis lacement without materially increasing t e dimensions and weight of the motor will be best understood from the following description when read in light of the accompanying drawings of a s ific embodiment of my invention selecte for illustrative purposes, while the scope of m invention will be more particularly pointe out in the appended claims. a In the drawings:

Fig. 1 is a diagram showing the connections of a motor according to my invention.

Fig. 2 is a diagram of a 4-pole three-phase rotor winding with a two-pole compensat 'i winding.

ig. 3 is a sectional view of the motor showing an arrangement of the compensatin winding within the rotor.

ig. 4 is an-elevation partly in section of a motor corresponding to the arrangement shown in Fig. 3.

It is well known that the phase-displacement of induction motors can be com ensated according to the method propose by Leblanc by connecting the induction motor in cascade with a second machine having an armature winding provided with a commutator and a number of brushes sliding thereon corresponding to the number of phases and connected with the brushes sliding on the slip-rings of the rotor of the induction motor. v

Such twin-machines had comparatively small opportunities owing to the increased costs and bulk, in spite of the increase of the power-factor having become a very imperious need. It may be understood, that in the current distribution plants the inductive load increases from day to day with respect to the resistive load owing to the rapid increase of the number of the motors used by the customers. Hence a considerable per- 1922. Serial No. 566,559.

centage of the load of the distributing plant consists of the wattlws currents hindering an economic utilization of the distributing plant.

As the majority of the motors causin the wattless currents are of small' or me 'um size, afl'ording no possibility at all of the Leblanc-method, it is very important to provide, a compensation of the phase-displacement increasing neither the bulk nor the costs of the'motors.

According to my invention I provide within the active iron besides the normalpolyphase rotor-winding connected with'the slip-rings, a winding connected to a commutator and designed for an output correspondin to the magnetizing energy of the motor, t e brushes of the commutator being connected to the polyphase winding of the rotor and means being provided to prevent the mutual induction of the two rotor wind infisahaving any detrimental effect.

ferring to Fig. l m is the three-phase 'll primary winding of the stator of the induction motor having the branches m m and m, fed from the line L, and 3 the t reephasesecondary winding of the rotor having the branches 3 3 and connected to the slip-rings 2,, 2,, 2,, respectively; nis the compensating commutator-winding of the rotor sharing the active iron with the rotor winding 3 and connected to the commutator k. b,, b b, are brushes corresponding to the three phases of the secondary winding y sliding on the commutator k and connected by means of the leads 9 to the brushes sliding on the slip-rings 2,, 2,, 2,.

It is essential that the ratio of the polenumbers of the induction motor and of the compensating winding should be either an even number or at least a fraction having an even number in its numerator or in its denominator. 95 Fig. 2 shows a dia am of the two rotor windings. The slip-ring winding of the r0.-' tor is a four-pole three-phase-wmding, the windings of the several phases 3/2 and being connected at their one en to the common neutral point 0 and; at their other end to the three slip-rings 2 .2 and 2, respectively.

The compensating winding n is a commutater-winding wound for two poles as will be seen from the one turn drawn with heavy lines.

The ratio of the two pole numbers 4:2 is an even number.

The rotor current with the slip-frequency is fed by means of the brushes 5,, b b, to the compensating winding n and will generate a magnetic field in the active-iron of the motor. Owing to the action of the commutator, the field generated by the compensating winding will revolve at slip frequency and will thus lag with respect to the commutator winding.

As however the compensating winding rotates with respect to the field generated by this winding with a speed exceeding the synchronism corresponding to the slip-frequency, the said field will induce electrometive forces in the compensating winding which will generate a wattless current in the circuit formed by the compensating winding, the brushes 6 6 leads g, sliprings z z and the secondary winding 3 of the rotor. If the ampere-turns resulting from this wattless current and the number of ampere turns of the rotor winding 3 are equal to the ampere turns due to the wattless component of the stator current if the motor is uncompensated the phasedisplacement will be totally compensated and the powerfactor is the unity. If the wattless ampereturns of the rotor are greater than the ampere-turns due to the entire wattless component of the stator current, the motor will be over-compensated, so that the motor will deliver into the line L a leading wattless current and improve the power-factor of the line.

The mutual induction of the two rotor windings may be eliminated by using different numbers of poles for the two windings, the ratio of the said numbers of poles being an even one, for example, 4:2, as in the described example.

The ratio of the pole-numbers is however not limited to an even number as it may be a fraction having but one even number either as numerator or as denominator. F or instance the motor may be wound for poles and the compensating winding for four poles giving a ratio 6:4= in no case can the ratio be an odd number f. i. 2:6 or 6:2:3.

To attain the above specified con'ipensation it is important that the saturation in the magnetic field generated by the ampere-turns of the compensating winding be high enough to secure substantially constant compensating E. M. forces throughout a large range of the load of the motor. Owing to the circumstauce that according to my invention the compensating field is superposed to the field of the induction motor, the said requirement is easily fulfilled.

With reference to Fig. 3, p are the slots of the stator receiving the primary winding m, and r are the slots of the rotor receiving the secondary or slip-ring winding 7 of the motor. at are channels arranged within the active iron of the rotor on a smaller radius, than the slots r. The compensating winding 01 is located in the said channels at.

As will be readily seen, only a part 8 of the flux generated by the compensatlng winding 77 is forced through the stator-iron, while the remainder s of the said flux will be closed through the zone between the slots 7* and the channels The advantages of this arrangement are the following:

As has been already stated, it is important to have a great saturation in the iron conducting the flux generated by the compensating winding. The saturation of the stator however cannot be a high one owing to the comparatively high frequency of the primary current. In the rotor the magnetization has a small frequency so that the iron losses are no hindrance to the saturation of the iron.

As the motors of smaller or medium size will be wound preferably for 4. poles and the compensatingwinding accordingly for 2 poles, the dimensions of the coil-heads will become substantially smaller by decreasing the diameter of the commutator-winding; hence the quantity of the copper required by the compensating winding will be diminished.

As the compensated motor according to Figs. 3 and 4 differs from the-normal type only in having an additional row of channels and a small commutator of few segments, requiring only very little space, a uniform f motor can b manufactured with the holes stamped into the iron lamellae used for the rotor. If it is not desired to provide for the compensation of the phase-displacement, the motor will be completed as an induction motor of the usual type, the channels m interfering in no way with its function, and improving the ventilation of the rotor. Tf over the compensation is required, it is only necessary to insert the turns of the compensating winding a into the channels :11 and to apply the commutator, for which the normal motor types afford enough place for the insertion of the commutator of very reduced dimensions.

The described compensation allows to increase the output of the motor with a slight plus of conductor material without increase of the dimensions of the iron.

Owing to the correction of the phase-displacement the number of slots provided for the windings can be substantially reduced with respect to the number of slots required in uncompensated motors, allowing a substantial increase in the amount of conducill tors placed in the iron of given diameter.- In this way the output of a motor of given iron dimensionscan be further increased.

The increase of output due to the compens sation will balance the costs of the additional compensating winding and of the commutator.

It will thus be seen that there are herein described induction-motors with compensa-- tion of the phase-displacement in which the several features of this invention are embodied and which obtain the various objects of my invention and are well suited to meet the requirement of practical use.

As many changes could be made in the above constructions and many a parently widely difl'erent embodiments of t is invention could be made without departin from the scope thereof, it is intended that a l matter contained in the above s ecification or shown in the accompanying rawings shall be interpreted as illustrative and not in a limiting sense.

Thus the three-phase windings may be in delta connection, further the stator of the,

motor may be provided with a single-phase primary winding and the secondary winding of the rotor may be a two, three or other polyphase winding.

Having now fully described and ascertained my said invention and the manner in which it is to be performed, I declare, that what I claim is:

1. In an asynchronous induction machine, a stator, a rotor, a polyphase rotor winding for the rotor and connected with slip-rings,

-' a commutator winding and commutator arranged on the rotor, brushes placed in. polyphase arrangement for co-operating with the said commutator, brushes for co-operating with the said slip-rings, means connecting the brushes associated with the slip-rings with the brushes associated with the commutator, and means to reduce the mutual induction of the two rotor windings.

2. In an asynchronous induction machine, a stator, a rotor, a polyphase rotor winding for the rotor and connected with slip-rings, a commutator winding arranged on v t e rotor, a commutator, brushes in polyphase arrangement for co-op'erating with the said commutator, brushes for co-operating with the said slip-rings, means connecting the brushes associated with the slip-rings to the brushes associated with thecommutator, the ratio of the numbers of poles of the two said rotor windings being an even integer or a fraction, which, when reduced to its lowest terms has either the numerator or denominator even.

3. In an alternating current induction motor, a stationary and a rotary active iron body constituting respectively, a stator and a rotor, a rimary motor winding on the stator, a po yphase secondary motor windcommutator and connected to the several phases of the polyphase rotor winding.

4. ,In an asynchronous induction machine, a stator, a rotor, a polyphase rotor winding connected with slip-rings, a commutator winding having a number of ampere turns to correspond substantially to the ampere turns due to the wattless current of the stator, said commutator winding being arranged .on the said rotor, a commutator,

brushes in polyphase arrangement for cooperating with the said commutator, brushes for co-operating with the said slip-rings, means connecting the brushes associated with the sliprings to the brushes associated With the commutator, and means to reduce the mutual induction of the two rotor windings.

5. In an asynchronous induction machine, a stator, a rotor, a polyphase rotor winding for the rotor and connected with sliprings, a commutator, a commutator winding having a number of ampere turns to correspond substantially to the ampere turns due to the wattless current of the stator, said commutator winding being arranged on the said rotor, brushes in polyphase arrangement co-operating with the said commutator, brushes for co-operating with the said slip-rings, means to connect the brushes associated with the slip-rings, to the brushes associated with the commutator, and means to reduce the mutual induction of the two rotor windings to a value preventing undue sparking on the commutator.

6. In an asynchronous induction machine, a stator, a rotor, a polyphase rotor winding for the rotor and connected with sli rings, a commutator, a commutator win ing having a number of ampere turns to correspond substantially to the ampere turns due to the Wattles current of the stator,

said commutator winding being arranged on body, a primary motor-winding on the one between the motor winding and the compensating winding of the rotor, a commutator on the rotor mnnected to the said compensating winding and 'brushes sliding on the said commutator and connected to the several phases of the secondary motor winding.

8. An asynchronous induction machine having in combination, a stator, a stator winding, a rotor having an iron body, a polyphase rotor winding on said rotor a commutator winding on said rotor having its ampere turns substantially the same as the ampere turns of the stator winding corresponding to the wattless current of the stator winding, said commutator winding being within the active iron of said rotor body at a smaller radius than said; rotor winding and separated therefrom by an annular zone of iron, a commutator on said rotor for said commutator windings, brushes in polyphase arrangement cooperating with said commutator, and means including slip rings and cooperating brushes for connecting said brushes cooperating with said commutator to each phase of said rotor winding.

9. An asynchronous induction machine having in combination, a stator with a polyphase primary winding, a rotor carrying a polyphaserotor winding and a commutator winding, said commutator winding being separated from said rotor winding by a zone of iron and having its ampere turns substantially the same as the ampere turns of the stator windinfg corresponding to the wattless current 0 the stator winding, a commutator for said commutator winding having brushes in polyphase arrangement, and means including slip rings and brushes for connecting said brushes of said commutator with the respective phases of said rotor winding.

In testimon whereof I afiix my signature in presence 0 two witnesses.

DR. THEODORE TORDA. Witnesses CHARLES Macon, EUGENE Haasm. 

